Nostalgia for something that happened only a year ago must surely represent our accelerated culture reaching warp speed. But here we are: this week marks the first anniversary of the London Olympics, and the magic of that event and the subsequent Paralympics are once again being celebrated. "Will anything ever feel this good again?" read a wonderfully understated headline in Saturday's Telegraph. To which the answer is: perhaps not, but 120,000 tickets for this weekend's Anniversary Games sold out in 75 minutes, which suggests that even the idea of a brief rerun – to be staged at the Olympic Park, featuring Mo Farah and Usain Bolt, and sponsored by Sainsbury's – is a dependable winner.

One matter, though, seems much more uncertain. What happened to all that talk of a diverse Britain reborn, and a nation that had conclusively mastered the art of welcoming outsiders?

The archives are full of this stuff. Eddie Izzard claiming that thanks to the Games, people newly understood "what modern multicultural Britain is all about, and that obviously it is working"; the outgoing chair of the Equalities and Human Rights Commission Trevor Phillips citing "a profound sea-change in British attitudes to social diversity". In the wake of successes for Greg Rutherford, Jessica Ennis and Mo Farah, one of the most celebrated tweets during the Olympic fortnight read thus: "A ginger, a mixed-race woman and a one-time Somali refugee walk into a pub – and everyone buys them a drink."

Indeed, the day before the Olympics began, David Cameron puffed out his chest and claimed that "there is no more diverse, more open, more tolerant city in the world than this one". Strange that in the year since, he and his ministers have charged in the opposite direction, and their policies tend to suggest not the wonders of metropolitan openness and tolerance, but some mad checklist drawn up by Daily Express headline writers.

There are plans for "bonds" – the exact charge to be levied remains unclear – to be imposed on visitors from such countries as India, Pakistan and Nigeria. No week must be allowed to go by without at least one minister insisting that newly arrived migrants must quickly learn to speak English, even as councils are forced to drastically reduce the requisite tuition. Catastrophic cuts to legal aid and an increasingly punitive benefits system speak for themselves. Meanwhile, by way of nasty mood music, the innocuous word "tourist" has been reinvented, to be used in pejorative new compound words: health-tourist, benefit-tourist, education-tourist.

There are two reasons for this. First, much of this is less about the practicalities of policy than how well such proposals might play with the kind of voters whose supposed views are currently being channelled by Lynton Crosby. In any case, if you increasingly feel the overall aim of government is to make immigrants' lives as difficult as possible, you're not mistaken. It is.

Ten days ago, the former Lib Dem education minster Sarah Teather broke cover, and talked not only about initial Tory intentions to restrict the bringing-in of non-European spouses to people earning £40,000 a year or more, but a new subcommittee of government called the Inter Ministerial Group on Migrants' Access to Benefits and Public Services. No cabinet ministers attends its meetings, but it apparently includes such figures as the Lib Dem education minister David Laws and the Tory immigration minister Mark Harper, and its fingerprints are all over many of the proposals above.

In March, leaked emails suggested that the group considered banning the children of illegal immigrants from British schools, before civil servants from the Department for Education pointed out that such a move would contravene the UN charter on the rights of the child; it has also worked on beefing up the link between housing and so-called local links. As Teather revealed, it was not only set up at the "explicit insistence" of Cameron, but originally called the Hostile Environment Working Group, a title that starkly announced its intentions for "unwanted" immigrants. So, back to the PM's words from last summer: "There is no more diverse, more open, more tolerant city in the world than this one." Really?

It would be dishonest to discuss all this without a mention of the general public. Perhaps things are just as Cameron, Laws, Harper et al evidently think. Given that the summer of the Olympics and Paralympics was eventually followed by the Ukip spring, maybe many of the same people who came together to cheer on Team GB also support creating a system that encourages people to think the worst of anyone from outside the UK. It is increasingly leaving vulnerable people drowning in impenetrable paperwork, and threatening even people given leave to remain with destitution.

There again, no one – least of all any front-rank Labour politician – has yet been bold enough to explain that there's a glaring gap between the cant we heard last summer, and where Britain has subsequently arrived. Put another way, if you want the same kind of society that delivers not just wondrous sporting events but no end of vital businesses and services, the Hostile Environment route really isn't the greatest way to go. That's the utilitarian argument – it'd also be nice to think that someone might also come along and remind us of our common humanity.

Mo Farah will be running in the 3,000m this weekend, and perhaps commentators will once again go through his uncertain backstory. No one seems sure how and when he came to the UK. He may have come to join his father, who had claimed asylum; other accounts have him arriving with his mother and a younger brother. Some say he stopped here en route to his grandmother in Holland, and decided to stay. The details are uncertain because that's what labyrinthine immigration systems and complex journeys across continents do to people. But here's a question: had ministers put up the kind of hateful machinery that is now being assembled at speed, how exactly do you think he would have got on?